A possible role of inwardly rectifying k+ channels in chick myoblast differentiation. Shin, Ki Soon, Jae-Yong Park, Hyockman Kwon, Chin Ha Chung, and Man -Sik Kang. Department of Molecular Biology and Research Center for Cell Differentiation, Seoul National University, Seoul 151-742, Korea
APStracts 3:0359C, 1996.
We examined the developmental change of inwardly rectifying K+ channels (IRK) and its possible role in myogenesis. Northern blot analysis revealed the increase in the level of IRK mRNA during myogenesis. Accordingly, the IRK current was not detectable in replicating myoblasts but appeared first in aligned myoblasts that were competent for fusion, and gradually increased thereafter. The time course change of IRK activity was closely related to the increase in resting membrane potential during myogenesis. Application of 0.5 mM Ba2+ to the bath depolarized the membrane and blocked IRK currents dramatically but not outwardly rectifying K+ currents. Myoblasts devoid of IRK had low resting K+ permeability, whereas myotubes that possess IRK had high resting K+ permeability. In some aligned myoblasts, anomalous hyperpolarization was elicited by increasing [K]o, which may be attributable to the increased conductance of IRK. Noteworthy was the fact that maximum fusion was obtained at this range of K+ concentration. These findings imply that IRK is responsible for the change in the K+ permeability during chick myogenesis, which may provide a larger driving force for Ca2+ influx that is a prerequisite for myoblast fusion. 

Received 6 May 1996; accepted in final form 8 October 1996.
APS Manuscript Number C240-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 November 1996